1. Field of the Invention
The invention relates to a method for the wet-chemical treatment of a semiconductor wafer.
2. Background Art
Semiconductor wafers required for producing electronic components regularly have to be cleaned of particles and metal contaminants. Such cleaning steps are customary, and are performed both by the manufacturers of the electronic components and by the suppliers thereof: the manufacturers of the semiconductor wafers. Individual-wafer cleaning and batch cleaning methods are known. The present invention relates to individual-wafer cleaning methods.
Individual-wafer cleaning is based on the principle of a rotating semiconductor wafer, wherein a liquid film forms on the surface of the semiconductor wafer which is to be cleaned. Individual-wafer cleaning is advantageous for numerous reasons, one such reason being a smaller consumption of cleaning liquid. Aqueous solutions containing hydrogen fluoride (HF) and ozone (O3) have proven to be effective cleaning liquids, see e.g. U.S. Pat. No. 5,759,971.
U.S. Pat. No. 7,037,842 B2 describes a method in which a surface of a rotating semiconductor wafer is sprayed with an aqueous cleaning liquid containing e.g. HF and O3. By way of example, hydrogen (H2) and nitrogen (N2) are also known as alternative constituents of the cleaning liquid.
U.S. Pat. No. 7,021,319 B2 discloses exposing the rotating semiconductor wafer to sound waves in order to increase the effectiveness of the cleaning process. In the center of the semiconductor wafer rotating about its central axis, a bulge of the liquid film occurs on account of the surface tension and the vanishing centrifugal force there, which can be reduced by adding an alcohol and reducing the surface tension. As an alternative, the bulge is reduced by physical forces, for example by blowing N2 gas onto the bulge.
A suitable apparatus for carrying out an individual-wafer cleaning method is described in US 2002/0050279 A1. The systems of the design series Raider SP from Semitool/USA are particularly well suited for these methods. US 2002/0050279 A1 also discloses a method which serves to enable sufficient diffusion of a gas through a liquid film applied to a rotating semiconductor wafer. The thickness of the liquid film is reduced by the fast rotation of the semiconductor wafer. The thinner the film, the faster a gas can diffuse through the film. However, for this reason, the thickness of the liquid film is a limiting parameter for the concentration of the gas component on the surface of the semiconductor wafer.